The present application relates to a bi-directional optical circulator, and in particular to a bi-directional wavelength interleaving optical circulator for directing signals with channels from a first set of channels in one direction, while directing signals with channels from a second set of channels in another direction.
Conventional optical circulators, such as the one disclosed in U.S. Pat. No. 5,204,771 issued Apr. 20, 1993 in the name of Masafumi Koga, rely on reciprocal and non-reciprocal rotators as well as birefringent crystals to alter the polarization of sub-beams and direct them to the appropriate output port. In conventional circulators, illustrated conceptually in FIG. 1, signals entering a first port 1 are output a second port 2, while signals entering the second port 2 are output a third port 3. Systems that have optical traffic traveling in both directions, i.e. from the third port to the second port, and from the second port to the first port, require a second circulator to accommodate the second stream of signals.
An object of the present invention is to provide a bi-directional optical circulator for circulating two different sets of optical channels in opposite directions.
Accordingly, the present invention relates to a bi-directional circulator device comprising:
a first port for inputting a first signal comprising at least one channel from a first set of channels, and for outputting a second signal comprising at least one channel from a second set of channels, which is independent of the first set of channels;
a second port for inputting a third signal comprising at least one channel from the first set of channels, for inputting the second signal comprising at least one channel from the second set of channels, for outputting the first signal comprising at least one channel from the first set of channels, and for outputting a fourth signal comprising at least one channel from the second set of channels;
a third port for inputting the fourth signal comprising at least one channel from the second set of channels, and for outputting the third signal comprising at least one channel from the first set of channels;
wavelength-selective polarization-rotating means optically coupled to the first, second and third ports for rotating the polarization of the channels in one of the first or the second set of channels, while having no cumulative effect on the polarization of the channels in the other set of channels; and
polarization-dependent signal directing means for directing the first and third signals exiting the wavelength-selective polarization-rotating means to the second and the third ports, respectively, and for directing the second and fourth signals exiting the wavelength-selective polarization-rotating means to the first and the second ports, respectively.
Another aspect of the present invention relates to A four port closed optical circulator device comprising:
a first port for inputting a first signal comprising at least one channel from a first set of channels or for inputting a second signal comprising at least one channel from a second set of channels, which are independent from the first set of channels, said first port comprising first polarizing means for orienting the first and second signals with a first polarization;
a second port for inputting a third signal comprising at least one channel from the first set of channels or for inputting a fourth signal comprising at least one channel from the second set of channels, said second port comprising a second polarizing means for orienting the third and fourth signals with the first polarization;
a third port for inputting a fifth signal comprising at least one channel from the first set of channels or for inputting a sixth signal comprising at least one channel from the second set of channels, said third port comprising a third polarizing means for orienting the fifth and sixth signals with a second polarization, which is orthogonal to the first polarization;
a fourth port for inputting a seventh signal comprising at least one channel from the first set of channels or for inputting an eighth signal comprising at least one channel from the second set of channels, said fourth port comprising a fourth polarizing means for orienting the seventh and eighth signals with the second polarization;
wavelength-selective polarization-rotating means optically coupled to the first, second, third and fourth ports for rotating the polarization of the channels in one of the first or the second set of channels, while having no substantial cumulative effect on the polarization of the channels in the other set of channels;
first beam directing means for directing the first, second, fifth and sixth signals along a main optical path through the wavelength-selective polarization rotating means, for directing the fourth and seventh signals to the first port, and for directing the third and eighth signals to the third port;
second beam directing means for directing the third, fourth, seventh and eighth signals along the main optical path through the wavelength-selective polarization rotating means in a direction opposite to the first, second, fifth and sixth signals, for directing the first and sixth signals to the second port, and for directing the second and fifth signals to the fourth port; and
non-reciprocal polarization rotating means for rotating the polarization of the third, fourth, seventh and eighth signals by 90xc2x0, while having no cumulative effect on the first, second, fifth and sixth signals.